Variation on the "Two Trains" puzzle type

Two trains leave their stations heading to each other's starting station, travelling on parallel tracks in opposite directions. After the two trains cross paths, the first train takes one hour to reach it's destination, whilst the second train takes four hours to reach it's destination.

How much faster was the first train travelling in relation to the second train?

I've done a little model in Excel and it seems the answer is 2 times, but I'd like a formulaic solution to the problem.

Two trains leave their stations heading to each other's starting station, travelling on parallel tracks in opposite directions. After the two trains cross paths, the first train takes one hour to reach it's destination, whilst the second train takes four hours to reach it's destination.
I've done a little model in Excel and it seems the answer is 2 times, but I'd like a formulaic solution to the problem.